code: def _clean_col_data(column_data):
      column_data = [
          (arr if arr is not None else []) for arr in column_data
      ]
      column_data = [[str(x) for x in arr] for arr in column_data]
      return column_data
  
file_path: lightwood/lightwood/encoder/categorical/multihot.py
imports: import torch
  import numpy
  from lightwood.encoder import BaseEncoder
  from sklearn.preprocessing import MultiLabelBinarizer
label_desc: Use image node_id 2 for calling the MultiHotEncoder obj's underlying member method code with example usage: obj._clean_col_data(column_data) and returns: column_data